On this day in 1905, the world’s largest diamond is found. At the Premier Mine in Pretoria, South Africa, a 3,106-carat diamond is discovered during a routine inspection by the mine’s superintendent. Weighing 1.33 pounds, and christened the “Cullinan,” it was [the largest diamond ever found.

The Cullinan diamond is the largest rough gem-quality diamond ever found, at 3,106.75 carats (621.35 g).

The largest polished gem from the stone is named Cullinan I or the Great Star of Africa, and at 530.4 carats (106.1 g) was the largest polished diamond in the world until the 1985 discovery of the Golden Jubilee Diamond, 545.67 carats (109.13 g), also from the Premier Mine. Cullinan I is now mounted in the head of the Sceptre with the Cross. The second largest gem from the Cullinan stone, Cullinan II or the Lesser Star of Africa, at 317.4 carats (63.5 g), is the fourth largest polished diamond in the world. Both gems are in the Crown Jewels of the United Kingdom.

Sir William Crookes performed an analysis of the Cullinan diamond before it was cut and mentioned its remarkable clarity, but also a black spot in the middle. The colours around the black spot were very vivid and changed as the analyzer was turned. According to Crookes, this pointed to internal strain. Such strain is not uncommon in diamonds.

The stone was bought by the Transvaal government and presented to King Edward VII on his birthday. It was cut into three large parts by Asscher Brothers of Amsterdam, and eventually into 9 large gem-quality stones and a number of smaller fragments. At the time, technology had not yet evolved to guarantee quality of the modern standard, and cutting the diamond was considered difficult and risky. In order to enable Asscher to cut the diamond in one blow, an incision was made, half an inch deep. Then, a specifically designed knife was placed in the incision and the diamond was split in one heavy blow. The diamond split through a defective spot, which was shared in both halves of the diamond.

41 – After a night of negotiation, Claudius is accepted as Roman Emperor by the Senate.

1348 – A strong earthquake strikes the South Alpine region of Friuli in modern Italy, causing considerable damage to buildings as far away as Rome.